+The **Oligocene** epoch (33.9 to 23.03 million years ago) marked a transition in Earth's climate, seeing a global cooling trend and the expansion of open [Grasslands](/wiki/grasslands). This period, nestled between the [Eocene](/wiki/eocene) and [Miocene](/wiki/miocene) epochs, witnessed the diversification of early mammals and the spread of new plant life across continents.
+## See also
+- [Geologic Time](/wiki/geologic_time)
+- [Cenozoic Era](/wiki/cenozoic_era)
+- [Paleogene Period](/wiki/paleogene_period)
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